Virus resistant plants expressing animal cell-derived (2′-5′)oligadenylate synthetase and ribonuclease L and A method for creating the same

ABSTRACT

The present invention relates to a method for creating a plant having resistance to RNA viruses, comprising incorporating a DNA sequence encoding an animal cell-derived (2′-5′)oligoadenylate synthetase and a DNA sequence encoding an animal cell-derived ribonuclease L into a chromosome(s) of the plant and expressing the DNA sequences, as well as plants created by the above method. The present invention is widely applicable to the breeding of virus resistant plant varieties.

TECHNICAL FIELD

The present invention relates to a technology for creating a virus resistant plant expressing an animal cell-derived (2′-5′) oligoadenylate synthetase and an animal cell-derived ribonuclease L using recombinant DNA technology. More specifically, the present invention relates to a method for creating a plant having resistance to viruses, comprising incorporating DNA sequences encoding an animal cell-derived (2′-5′)oligoadenylate synthetase and an animal cell-derived ribonuclease L into a chromosome(s) of the plant and expressing the DNA sequences; and a virus resistant plant obtained by the above method.

BACKGROUND ART

Viruses are one of the major stress sources for plants. It is not seldom that crop-producing districts shift or cultivars are renewed due to damage from viral diseases. At present, there is no effective drug that acts on viruses directly. Thus, plants infected with viruses are subjected to incineration. Although virus resistance is an important goal for breeding, it has been impossible to rear a virus resistant cultivar with conventional breeding technologies such as crossing where a source of a resistance gene cannot be found in wild-type or related species.

As a method for supplementing such conventional breeding technologies, a method have been developed recently in which virus resistance is conferred on plants using recombinant DNA technology. Recombinant DNA technology has made gene transfer possible which goes beyond the deadlock of conventional crossing described above. Furthermore, this technology allows to introduce into existing cultivars a virus resistance gene alone and, thus, it has become possible to save the time required for breeding greatly.

As a method for creating virus resistant plants using recombinant DNA technology, methods of expressing a gene encoding a virus coat protein or a viral replication protein, an antisense gene, and a gene encoding a satellite RNA, and the like have been reported (see, for example, Arch. Virol., 115, 1, 1990). These methods confer resistance to only one kind of virus or its related viruses alone. A method for conferring resistance to various kinds of viruses is still under development.

As a method for conferring resistance to a large number of viruses at the same time, a method using a double-stranded RNA specific ribonuclease (International Publication WO93/20686) and a method using a (2′-5′)oligoadenylate synthetase (Bio/Technology, 11, 1048, 1993) have been reported.

With respect to the method using a (2′-5′)oligoadenylate synthetase, it has been reported that the virus resistance in the resultant transformant plants is extremely weak (The Proceedings of XVIIIth Eucarpia Symposium, Section Ornamentals, 1995). Briefly, a (2′-5′)oligoadenylate synthetase was introduced into a tobacco plant (cv Samsun) and then the tobacco mosaic virus (hereinafter referred to as “TMV”) OM strain was inoculated into the resultant plant expressing the (2′-5′)oligoadenylate synthetase. As a result, no delay in the development of disease symptoms was recognized as compared to controls. Also, there have been many reports that the existence of ribonuclease L-like molecules are not recognized in plant cells (Biochem. Biophys. Res. Commun., 108, 1243, 1982; J. Biol. Chem., 259, 3482, 1984; The Proceedings of XVIIIth Eucarpia Symposium, Section Ornamentals, 1995).

DISCLOSURE OF THE INVENTION

The present inventors have made intensive and extensive researches expecting that, by expressing both an animal cell-derived (2′-5′)oligoadenylate synthetase gene and an animal cell-derived ribonuclease L gene in a plant, virus resistance will be remarkably increased compared to that obtained by the expression of a (2′-5′) oligoadenylate synthetase gene alone. Thus, the present invention has been achieved.

The present invention relates to a method for creating a plant having resistance to RNA viruses, comprising incorporating a DNA sequence encoding an animal cell-derived (2′-5′)oligoadenylate synthetase (hereinafter referred to as “2-5Aase”) and a DNA sequence encoding an animal cell-derived ribonuclease L (hereinafter referred to as “RNaseL”) into a chromosome(s) of the plant and expressing the DNA sequences; and a virus resistant plant created by the above method.

Hereinbelow, the present invention will be described in detail.

(1) DNA Sequences Encoding 2-5Aase and RNaseL, Respectively

The presence of a 2-5Aase/RNaseL system in animal cells has been known as partly contributing to the anti-virus state induced by interferon (Annu. Rev. Biochem., 51, 251, 1982). 2-5Aase protein is a protein having an enzymatic activity to synthesize (2′-5′) oligoadenylate (usually a trimer or tetramer; hereinafter referred to as “2-5A”) from its substrate adenosine triphosphate (ATP) when activated upon recognition of double-stranded RNA. A cDNA encoding 2-5Aase has been cloned from human (EMBO J., 4, 2249, 1985), mouse (J. Biol. Chem., 266, 15293, 1991; Nuc. Acids. Res., 19, 1919, 1991) and rat (EMBL Acc. No. Z18877). This time, the present inventors have succeeded in cloning a cDNA encoding 2-5Aase from bovine. Other DNA sequences encoding 2-5Aase may also be used in the present invention as long as they can provide the above-described 2-5Aase activity. In other words, DNA sequences encoding 2-5Aase cloned from animal species other than those enumerated above, and even the above DNA sequences having replacement, deletion, addition or insertion in the encoded amino acids may also be used in the present invention as long as they can provide the above-described 2-5Aase activity. RNaseL protein is a protein which has an activity to bind with 2-5A and which exhibits RNA degradation activity upon binding with 2-5A. A cDNA encoding RNaseL has been cloned from human (Cell, 72, 753, 1993). Also, the present inventors have succeeded this time in cloning a cDNA encoding RNaseL from bovine. Other DNA sequences encoding RNaseL may also be used in the present invention. DNA sequences encoding RNaseL cloned from animal species other than those mentioned above, and even the above DNA sequences having replacement, deletion, addition or insertion in the encoded amino acids may also be used in the present invention as long as they can provide the above-described RNaseL activity.

In the Examples described below, human- or bovine-derived cDNA clones are used as DNA sequences encoding 2-5Aase and RNaseL. Needless to say, however, DNA sequences encoding 2-5Aase and RNaseL which may be used in the present invention are not limited to these human- or bovine-derived 2-5Aase and RNaseL.

In general, when a DNA sequence is coding for a polypeptide having an amino acid sequence, there exist a plurality of DNA sequences (degenerate isomers) corresponding to the single amino acid sequence because there exist a plurality of genetic codes (codons) corresponding to an amino acid. In the DNA sequences encoding 2-5Aase and RNaseL used in the present invention, it is needless to say that any genetic code may be used as long as it does not alter the amino acid sequence of the polypeptide encoded by the DNA sequence.

(2) Expression of DNA Sequences Encoding 2-5Aase and RNaseL, Respectively

In order for DNA sequences encoding 2-5Aase and RNaseL, respectively, to be expressed in a transgenic plant, at least these DAN sequences must be transcribed into RNAS. When a foreign gene is incorporated in a plant chromosome, it is known that such a gene is incorporated into a transcription region on the chromosome with a certain probability (EMBO J., 6, 3891, 1987). Therefore, it is possible to incorporate a DNA sequence encoding 2-5Aase or RNaseL alone into a plant chromosome and to express it in the plant. However, it is preferable to incorporate such a DNA sequence after ligating thereto appropriate promoter and terminator sequences.

In this case, as a promoter, any promoter which has been known to function in plant cells may be used. Specific examples include a promoter for a gene encoding ribulose-1,5-bisphosphate carboxylase small subunit; a promoter for nopaline synthetase gene; a promoter allowing production of cauliflower mosaic virus 35S-RNA (CaMV 35S promoter) (Proc. Natl. Acad. Sci. USA, 83, 2358, 1986; Plant Cell Rep., 4, 355, 1985; Cell, 30, 763, 1982; Nature, 313, 810, 1985) and the like. As a terminator, any terminator which has been known to function in plant cells may be used. Specific examples include a terminator for nopaline synthetase gene; a terminator for octopine synthetase gene (J. Mol. Appl. Gen., 1, 561, 1982; EMBO J., 3, 835, 1984) and the like.

(3) Incorporation of DNA Sequences Encoding 2-5Aase and RNaseL into a Plant

For the introduction of a DNA sequence encoding 2-5Aase or RNaseL various methods already reported and established may be used. For example, a method using the Ti plasmid of Agrobacterium tumefaciens as a vector, a method of introducing a DNA sequence directly into plant sections or plant protoplasts, or the like may be used depending on the plant species of interest (see, for example, “Plant Genetic Transformation and Gene Expression; A Laboratory Manual”, Draper, J. et al., Blackwell Scientific Publications, 1988). By tissue culturing the transformed plant tissues or cells under appropriate conditions for the plant species, the transformed plant can be regenerated. As a method for obtaining a transformed plant which expresses 2-5Aase simultaneously with RNaseL, a method may be considered which comprises examining the expression of each of the genes of interest in 2-5Aase-introduced plant and RNaseL-introduced plant and crossing a plant expressing 2-5Aase with a plant expressing RNaseL. Alternatively, a 2-5Aase- or RNaseL-introduced transformant plant may be re-transformed with RNaseL gene or 2-5Aase gene, respectively. It is also possible to transform a plant with both 2-5Aase gene and RNaseL gene at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.

FIG. 1 is a diagram showing vectors for plant transformation which individually comprise a human-derived 2-5Aase cDNA or a human-derived RNaseL cDNA, respectively.

NOSpro: nopaline synthetase gene promoter

NOSterm: nopaline synthetase gene terminator

CaMV35S: cauliflower mosaic virus 35S promoter

NPTII: neomycin resistance gene

HYG: hygromycin resistance gene

2-5Aase: 2-5Aase cDNA

RNaseL(T): partial length RNaseL CDNA

RNaseL(F): full length RNaseL cDNA

RB: right border

LB: left border

FIG. 2 is a graph showing the activity of 2-5Aase in leaves of a 2-5Aase-introduced transformant tobacco plant (cv Xanthi nc).

Control: non-transformant

2-5Aase#11b: transformant

2-5Aase#12a: transformant

2-5Aase#13b: transformant

FIG. 3 is a graph showing the activity of RNaseL in leaves of a partial length RNaseL-introduced transformant tobacco plant (cv Xanthi nc).

Control: non-transformant

RNaseL#H1: transformant

RNaseL#H2: transformant

RNaseL#H3: transformant

RNaseL#H4: transformant

Spleen: crude extract from mouse spleen

FIG. 4 is a graph showing the activity of RNaseL in leaves of a full length RNaseL-introduced transformant tobacco plant (cv Xanthi nc).

Control: non-transformant

RNaseL(F)#23a: transformant

RNaseL(F)#14a: transformant

RNaseL(F)#27a: transformant

RNaseL(F)#12b: transformant

RNaseL(F)#30b: transformant

Spleen: crude extract from mouse spleen

FIG. 5 is a graph showing ratios (%) of the 2-5Aase-introduced tobacco (2-5Aase#11b) individuals and [2-5Aase+partial length RNaseL]-introduced tobacco (2-5Aase#11b+RNaseL#H1, 2-5Aase#11b+RNaseL#H4) individuals in which uninoculated upper leaves exhibited disease symptoms after CMV (Y strain) inoculation.

FIG. 6 is a photograph showing the results of electrophoresis to detect CMV coat protein in CMV (Y strain)-inoculated tobacco leaves.

2-5Aase#11b: 2-5Aase-introduced tobacco

2-5Aase#11b+RNaseL#H4: [2-5Aase+partial length RNaseL]-introduced tobacco

FIGS. 7A and 7B show photographs of plant morphologies exhibiting the presence or absence of necrotic spots in 2-5Aase+RNaseL (F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL (F)-introduced tobacco 3 days after inoculation with CMV Y strain.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F) #23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#27a

F. RNaseL(F)#27a

G. 2-5Aase#13b

H. 2-5Aase#13b+RNaseL(F)#30b

I. RNaseL(F)#30b

↑ Inoculated leaves

FIGS. 8A and 8B show photographs of plant morphologies exhibiting the presence or absence of systemic symptoms in 2-5Aase+RNaseL(F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 12 days after inoculation with CMV Y strain.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F)#23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#27a

F. RNaseL(F)#27a

G. 2-5Aase#13b

H. 2-5Aase#13b+RNaseL(F)#30b

I. RNaseL(F)#30b

FIG. 9 is a photograph showing the results of electrophoresis to detect CMV in portions with no necrotic spots in inoculated leaves exhibiting necrotic spots in various transformant tobacco plants 5 days after inoculation.

1. 2-5Aase#13b

2. RNaseL(F)#23a

3. 2-5Aase#13b+RNaseL(F)#23a: portion with necrotic spot formation

4. 2-5Aase#13b+RNaseL(F)#23a: portion without necrotic spots

5. RNaseL(F)#30b

6. 2-5Aase#13b+RNaseL(F)#30b: portion with necrotic spot formation

7. 2-5Aase#13b+RNaseL(F)#30b: portion without necrotic spots

8. RNaseL(F)#27a

9. 2-5Aase#13b+RNaseL(F)#27a: portion with necrotic spot formation

10. 2-5Aase#13b+RNaseL(F)#27a: portion without necrotic spots

FIG. 10 is a photograph showing the results of electrophoresis to detect CMV in uninoculated upper leaves in various transformant tobacco plants 12 days after inoculation.

1. Non-transformant

2. 2-5Aase#13b

3. RNaseL(F)#23a

4, 5 2-5Aase#13b+RNaseL(F)#23a

6 RNaseL(F)#27a

7, 8 2-5Aase#13b+RNaseL(F)#27a

9 RNaseL(F)#30b

10, 11 2-5Aase#13b+RNaseL(F)#30b

FIG. 11 shows photographs of plant morphologies exhibiting the presence or absence of necrotic spots in 2-5Aase+RNaseL (F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL (F)-introduced tobacco 5 days after inoculation with a crude extract from CMV Y strain-infected leaves.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F)#23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#30b

F. RNaseL(F)#30b

↑ Inoculated leaves

FIG. 12 shows photographs of plant morphologies exhibiting the presence or absence of systemic symptoms in 2-5Aase+RNaseL (F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL (F)-introduced tobacco 16 days after inoculation with a crude extract from CMV Y strain-infected leaves.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F)#23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#30b

F. RNaseL(F)#30b

FIG. 13 shows photographs of plant morphologies exhibiting the presence or absence of necrotic spots in 2-5Aase+RNaseL (F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL (F)-introduced tobacco 5 days after inoculation with a crude extract from PVY T strain-infected leaves.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL (F) #23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#30b

F. RNaseL(F)#30b

↑ Inoculated leaves

FIGS. 14A and 14B show photographs of plant morphologies exhibiting the presence or absence of systemic symptoms in 2-5Aase+RNaseL(F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 14 days after inoculation with a crude extract from PVY T strain-infected leaves.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F)#23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#27a

F. RNaseL(F)#27a

G. 2-5Aase#13b

H. 2-5Aase#13b+RNaseL(F)#30b

I. RNaseL(F)#30b

FIG. 15 shows photographs representing the results of electrophoresis to detect PVY T strain in uninoculated upper leaves 5 days after infection (A) and uninoculated upper leaves 10 days after infection (B) in various transformant tobacco plants.

1. Non-transformant

2, 3 2-5Aase#13b

4, 5 RNaseL(F)#23a

6, 7 2-5Aase#13b+RNaseL(F)#23a

8, 9 RNaseL(F)#30b

10,11 2-5Aase#13b+RNaseL(F)#30b

FIGS. 16A and 16B show photographs of plant morphologies exhibiting the presence or absence of necrotic spots in 2-5Aase+RNaseL(F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 3 days after inoculation with a crude extract from PVY O strain-infected leaves.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F)#23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#27a

F. RNaseL(F)#27a

G. 2-5Aase#13b

H. 2-5Aase#13b+RNaseL(F)#30b

I. RNaseL(F)#30b

↑ Inoculated leaves

FIGS. 17A and 17B show photographs of plant morphologies exhibiting the presence or absence of systemic symptoms in 2-5Aase+RNaseL(F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 15 days after inoculation with a crude extract from PVY O strain-infected leaves.

A. 2-5Aase#13b

B. 2-5Aase#13b+RNaseL(F)#23a

C. RNaseL(F)#23a

D. 2-5Aase#13b

E. 2-5Aase#13b+RNaseL(F)#27a

F. RNaseL(F)#27a

G. 2-5Aase#13b

H. 2-5Aase#13b+RNaseL(F)#30b

I. RNaseL(F)#30b

FIG. 18 shows photographs representing the results of electrophoresis to detect PVY O strain in inoculated leaves 5 days after inoculation (A) and uninoculated upper leaves 6 days after inoculation (B) in various transformant tobacco plants.

1. Non-transformant

2. 2-5Aase#13b

3. RNaseL(F)#23a

4, 5 2-5Aase#13b+RNaseL(F)#23a

6 RNaseL(F)#27a

7, 8 2-5Aase#13b+RNaseL(F)#27a

9. RNaseL(F)#30b

10, 11 2-5Aase#13b+RNaseL(F)#30b

FIGS. 19A through 19D show the base sequence of SEQ ID NO: 9 for a bovine 2-5Aase cDNA and an amino acid sequence deduced therefrom.

FIGS. 20A through 20F show the base sequence of SEQ ID NO: 10 for a bovine RNaseL cDNA and an amino acid sequence deduced therefrom.

FIG. 21 is a graph showing the activity of 2-5Aase in leaves of 2-5Aase-introduced transformant tobacco (cv Samsun).

Control: Non-transformant

#13-4: 2-5Aase-introduced transformant

#13-5: 2-5Aase-introduced transformant

#13-7: 2-5Aase-introduced transformant

#13-9: 2-5Aase-introduced transformant

#13-10: 2-5Aase-introduced transformant

#13-11: 2-5Aase-introduced transformant

FIG. 22 is a graph showing the activity of RNaseL in leaves of RNaseL (F)-introduced transformant tobacco (cv Samsun).

Control: Non-transformant

#57-4a: RNaseL(F)-introduced transformant

#57-6b: RNaseL(F)-introduced transformant

#57-11: RNaseL(F)-introduced transformant

#58-7: RNaseL(F)-introduced transformant

#58-11: RNaseL(F)-introduced transformant

#58-18: RNaseL(F)-introduced transformant

FIG. 23 shows photographs of plant morphologies exhibiting the presence or absence of necrotic spots in 2-5Aase+RNaseL(F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 3 days after inoculation with a crude extract from CMV Y strain-infected leaves.

A. 2-5Aase(S)#13-10

B. 2-5Aase(S)#13-10+RNaseL(S)#57-6b

C. RNaseL(S)#57-6b

↑ Inoculated leaves

FIG. 24 shows photographs of plant morphologies exhibiting the presence or absence of systemic symptoms in 2-5Aase+RNaseL(F)-introduced tobacco, 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 10 days after inoculation with a crude extract from CMV Y strain-infected leaves.

A. 2-5Aase(S)#13-10

B. 2-5Aase(S)#13-10+RNaseL(S)#57-6b

C. RNaseL(S)#57-6b

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

In the following Examples, human-derived cDNAs were used as DNA sequences for 2-5Aase and RNaseL, and CaMV 35S promoter was used as a promoter for expressing the above genes in plants. For the expression of the 2-5Aase cDNA, pBI121 vector (EMBO J., 6, 3901, 1987) was used after replacing its β-glucuronidase gene (β GUS) with the 2-5Aase cDNA. For the expression of the RNaseL cDNA, PBIB-HYG vector (obtained from Dr. Detlef Becker, Institute for Genetics, Cologne University) was used after introducing thereinto a DNA sequence obtained by ligating CaMV 35S promoter upstream of the 5′ end to RNaseL cDNA.

As a host plant to confirm the effect of the present invention, a tobacco cultivar (Xanthi nc) was used. By the Agrobacterium-mediated leaf disk method or electroporation using tobacco protoplasts, tobacco transformants were obtained from the above strain (“Plant Genetic Transformation and Gene Expression; A Laboratory Manual”, Draper, J. et al., Blackwell Scientific Publications, 1988).

The presence or absence of expression of the 2-5Aase or RNaseL cDNA in the transformants was examined by preparing crude extracts from transformant leaves and determining the 2-5Aase activity (J. Biol. Chem., 259, 1363, 1984) and the RNaseL activity (Anal. Biochem., 144, 450, 1985) separately.

A transformant tobacco expressing both the 2-5Aase cDNA and the RNaseL cDNA was obtained by crossing a tobacco plant expressing the 2-5Aase activity with a tobacco plant expressing the RNaseL activity. When a tobacco plant expressing 2-5Aase alone and a tobacco plant expressing both 2-5Aase and RNaseL were inoculated with cucumber mosaic virus (CMV Y strain), the latter plant exhibited a significantly higher virus resistance than the former plant.

EXAMPLE 1 Construction of Plasmids for Use in Creating Transformant Plants (FIG. 1)

Based on the DNA sequence (SEQ ID NO: 1) for the human-derived 2-5Aase described in Proc. Natl. Acad. Sci. USA, 80, 4904, 1983, a probe for CDNA cloning (SEQ ID NO: 2) was prepared. A library for cDNA cloning was prepared by treating HeLa cells (obtained from Assistant Professor Enomoto, Division of Physiochemistry, Department of Pharmacology, the University of Tokyo) with 200 units/ml of human β interferon (Paesel Lorei GMBH & CO., Frankfurt) for 12 hours, extracting mRNAs therefrom, preparing cDNAs from the mRNA using a Pharmacia CDNA synthesis kit, and ligating the cDNAs to Lambda gt10 vector. It has been reported that there are two 2-5Aase mRNAs (1.6 kb and 1.8 kb). For expression in plants, the cDNA corresponding to the 1.6 kb mRNA was used. A plasmid pBI2-5Aase for expression in plant was prepared by replacing β GUS in pBI121 with the 2-5Aase cDNA (EcORI fragment).

The human-derived RNaseL cDNA was obtained by preparing a probe (SEQ ID NO: 4) based on the DNA sequence (SEQ ID NO: 3) disclosed in Cell, 72, 753, 1993 and screening a human spleen cDNA library (Clontech) with the probe. From the human spleen cDNA library, two cDNA clones were obtained: a partial length clone (lacking C-terminal 61 amino acid residues) and a full length clone. To the N-terminal of each of these two RNaseL cDNAs (HindIII-EcoRI fragments), CaMV 35S promoter was ligated and then the resultant fragment was replaced with the HindIII-SacI fragment of PBIB-HYG vector, to thereby obtain plasmids for expression in plant. The plasmid containing the partial length RNaseL and the plasmid containing the full length RNaseL are designated pBIBRNaseL(T) and pBIBRNaseL(F), respectively.

EXAMPLE 2 Transformation of Tobacco Plants

Tobacco (Nicotiana tabacum) cv Xanthi nc was used for transformation. Plasmids pBI2-5Aase and pBIBRNaseL(F) shown in FIG. 1 were separately introduced into Agrobacterium tumefaciens LBA4404 strain by electroporation. Tobacco leaf sections were infected with the Agrobacterium by the leaf disk method and placed on MS-B5 medium [vitamin B5-added Murashige & Skoog basal medium (Physiol. Plant., 15, 473, 1962)] containing 250 μg/ml claforan, 100 μg/ml kanamycin or 20 μg/ml hygromycin to select transformants. When shoots appeared, plants were transferred to hormone-free MS medium to induce rooting. The resultant transformant plants were aseptically cultured in vitro in plant boxes. Then, after potting, they were self-pollinated or crossed (2-5Aase+RNaseL) to obtain R1 seeds.

Plasmid pBIBRNaseL(T) was introduced into protoplasts prepared from tobacco leaves by electroporation. Protoplasts were prepared from tobacco (cv Xanthi nc) mesophyll cells by treating them in an enzyme solution [1% Cellulase Onozuka RS (Yakult), 1% Driselase (Kyowa Hakko Kogyo), 0.1% Pectolyase (Seishin Pharmaceutical), 0.4 M D-mannitol (pH 5.7)] overnight at room temperature. The protoplasts were washed 3 times with cold 0.4 M D-mannitol, and 1×10⁸ protoplasts were suspended in 0.8 ml of an electroporation buffer (0.3 M D-mannitol, 5 mM 2-(N-morpholino)ethanesulfonic acid, pH 5.8, 70 mM KC1) containing about 10 g g of the DNA plasmid. Then, the suspension was transferred into an electroporation cuvette (Bio-Rad, 0.4 cm in width), and a voltage of 300 V was applied at a capacitance of 125μF. The electroporated protoplasts were cultured in 1% agarose-containing spheroplast medium (Murashige & Skoog medium containing 1% sucrose, 0.4 M D-mannitol, 0.2 μg/ml 2,4-dichlorophenoxyacetic acid) for one week at 28° C. under dark conditions. Subsequently, selection of transformants was performed with hygromycin (20 μg/ml). When shoots were formed in the resultant colonies, the colonies were transferred to a hormone-free medium to obtain transformant plants. The resultant transformant plants were aseptically cultured in vitro in plant boxes. Then, after potting, they were crossed with 2-5Aase-introduced plants to obtain F1 seeds.

EXAMPLE 3 Detection of 2-5Aase Activity in 2-5Aase-Introduced Transformant Tobacco (FIG. 2)

A crude extract was prepared from in vitro cultured tobacco leaves and interferon-treated HeLa cells separately by the method of Wells et al. (J. Biol. Chem., 259, 1363, 1984). After measurement of wet weight, leaves were crushed in liquid nitrogen. Then, an equal volume of a lysis buffer [0.5% Nonidet P-40, 90 mM KCl, 1 mM magnesium acetate, 10 mM Hepes, pH 7.6, 2 mM 2-mercaptoethanol, 20 μg/ml leupeptin, 50μg/ml bovine lung aprotinin, 50μM phenylmethyl-sulfonyl fluoride (PMSF), 50 μg/ml trypsin inhibitor] was added thereto, homogenized in a Teflon Pestle homogenizer and centrifuged at 15,000 rpm at 4° C. for 20 minutes twice to obtain the supernatant. To 1 ml of the thus obtained leaf crude extract (in the case of a crude extract from HeLa cells, the extract was diluted 10-fold with the lysis buffer), 40 μl of polyI:polyC cellulose suspension was added and reacted at 4° C. for 2 hours. Then, the reaction solution was washed 3 times by centrifugation with a washing buffer (20 mM Hepes, pH 7.0, 10 mM magnesium acetate, 5 mM KCl), suspended in 50 μl of a reaction mixture (20 mM Hepes, pH 7.0, 20% glycerol, 7 mM 2-mercaptoethanol, 2 mM ATP, 5 mM KCl, 10 mM magnesium acetate) containing 0.2 μl of ³²P-rATP (10 mCi/ml, 3000 Ci/mmol; NEN) and reacted at 30° C. overnight (for 16-20 hours). The ³²P-labelled oligoadenylate produced in the reaction solution was purified by the method of Wells et al. (J. Biol. Chem., 259, 1363, 1984) using DEAE cellulose. Then, the radioactivity was measured with a liquid scintillation counter. The polyI:polyC cellulose was prepared by the method of Wells et al. (J. Biol. Chem., 259, 1363, 1984). The amount of protein in the crude extract was determined with a protein assay kit from Bio-Rad.

2-5Aase-introduced transformants exhibited significantly higher activity than that of non-transformant. In the crude extract from interferon-treated HeLa cells, the amount of ATP intake was 219 nmol/mg protein/4 hours, showing much higher 2-5Aase activity than that in 2-5Aase-introduced tobacco plants.

EXAMPLE 4 Detection of RNaseL Activity in RNaseL-Introduced Transformant Tobacco (FIGS. 3 and 4)

A crude extract was prepared from in vitro cultured tobacco leaves and mouse spleens separately by the method of Silverman et al. (J. Biol. Chem., 263, 7336, 1988). After measurement of wet weight, leaves were crushed in liquid nitrogen. Then, an equal volume of a hypo buffer (0.5% Nonidet P-40, 20 mM Hepes, pH 7.6, 10 mM potassium acetate, 15 mM magnesium acetate, 1 mM dithiothreitol (DTT), 100μM PMSF, 20μg/ml leupeptin) was added thereto and homogenized with Polytron™. The homogenate was centrifuged twice at 15,000 rpm at 4° C. for 20 minutes and the supernatant was collected to obtain a crude extract. 2-5A (5′-triphosphate tetramer; Seikagaku Kogyo) cellulose and control (ATP) cellulose were prepared in substantially the same manner as described in Example 3 for polyI:polyC cellulose. To 1.0 ml of a tobacco leaf extract (0.5 ml in the case of full length RNaseL-introduced tobacco) or a mouse spleen extract (diluted 4-fold with the hypo buffer), 2.5 μl of 0.1 M ATP and 7.5 μl of 3 M KCl were added and mixed with 25 μl of ATP cellulose suspension. The mixture was reacted at 4° C. for 1 hour and then centrifuged to collect the supernatant. To the supernatant, 25 μl of 2-5Aase cellulose suspension was added and reacted at 4° C. for 2 hours. Then, the supernatant was discarded. The ATP cellulose and 2-5Aase cellulose centrifuged and precipitated after reaction were separately washed 3 times by centrifugation with buffer A (11.5 mM Hepes, pH 7.6, 104 mM KCl, 5.8 mM magnesium acetate, 8.8 mM 2-mercaptoethanol, 10 μM PMSF, 20 μg/ml leupeptin) and suspended in 50 μl of buffer A. A ³²p-labelled polyU substrate was prepared by the method of Silverman (Anal. Biochem., 144, 450, 1985). 20 μl of the above suspension and 20 μl of a reaction solution (4 μl of 100 μM 2-5A, 2 μl of 5×buffer A, 0.25 μl of ³²P-polyUpCp, 0.05 μl of 10 μM cold polyu, 13.7 μl of water) were mixed and reacted at 37° C. overnight (for 16 hours). Then, the reaction was terminated by adding 50 μl of 10 mg/ml yeast RNA and 1 ml of trichloroacetic acid (TCA). The reaction solution was left on ice for more than 15 minutes. Thereafter, the TCA-insoluble fraction was trapped on Whatman GF/C filter and the radioactivity thereof was measured with a liquid scintillation counter. 2-5A dependent RNase activity (i.e., RNaseL activity) was expressed as a difference obtained by subtracting the radioactivity of 2-5A cellulose fraction from the radioactivity of ATP cellulose fraction. The amount of protein in the crude extract was determined with a protein assay kit from Bio-Rad. While the non-transformant tobacco exhibited an activity value below 0 (zero), partial length RNaseL-introduced transformants exhibited positive values (FIG. 3). Full length RNaseL-introduced transformants exhibited still higher activity than that of partial length RNaseL-introduced transformants (FIG. 4).

EXAMPLE 5 Cucumber Mosaic virus (CMV Y Strain) Infection Experiment(FIGS. 5 and 6)

R1 seeds (2-5Aase-introduced tobacco and 2-5Aase+RNaseL(T)-introduced tobacco) were sown on MS agar medium containing 800 μg/ml kanamycin or 800 μg/ml kanamycin+100 μg/ml hygromycin to select 2-5Aase-introduced plants or 2-5Aase+RNaseL-introduced plants, respectively. After potting the young plants, DNA was extracted from a part of their leaves (Nuc. Acids Res., 21, 4153, 1993). Then, the presence of 2-5Aase cDNA or RNaseL cDNA was confirmed by PCR. To plants about 2 weeks after potting, 3 μg/ml of CMV Y strain was inoculated, and the development of disease symptoms after viral inoculation was observed. For each transformant, 5 individuals were used. The ratio of plants exhibiting disease symptoms after inoculation in their uninoculated upper leaves was shown in percent. 2-5Aase+RNaseL(T)-introduced tobacco obtained by crossing the activity-confirmed, partial length RNaseL-introduced tobacco (see Example 3 and FIG. 3) with 2-5Aase-introduced tobacco exhibited significantly stronger virus resistance than that of the transformant tobacco into which only 2-5Aase was introduced (FIG. 5). Eight days after inoculation, uninoculated upper leaves were cut off from 5 individuals of each transformant tobacco (2-5Aase#11b and 2-5Aase#11b+RNaseL#H4) and the total protein was extracted therefrom with 5 volumes of SDS buffer (2% SDS, 80 mM Tris-HCl, pH 6.8, 2% 2-mercaptoethanol, 10% glycerol). Each of the thus obtained sample was diluted 100-fold with SDS electrophoresis sample buffer, and a 10 μl aliquot was fractionated by SDS polyacrylamide gel electrophoresis. The protein was transferred onto a polyvinylidene difluoride (PVDF) membrane (Millipore) to detect CMV in infected plant leaves by color formation with anti-CMV rabbit serum (about 2000-fold dilution) and protein A-alkaline phosphatase. In uninoculated upper leaves of 2-5Aase#11b-introduced tobacco, a strong CMV accumulation was observed in all of the five individuals sampled. On the other hand, in 2-5Aase#11b+RNaseL#H4-introduced tobacco, CMV accumulation was observed only in two individuals out of the five (FIG. 6).

EXAMPLE 6 Cucumber Mosaic Virus (CMV Y Strain) Infection Experiment

R1 seeds [1 line of 2-5Aase-introduced tobacco (2-5Aase#13b); 3 lines of RNaseL(F)-introduced tobacco (RNaseL(F)#23a, RNaseL(F)#27a, RNaseL(F)#30b)]and F1 seeds [3 lines of 2-5Aase+RNaseL(F)-introduced tobacco (2-5Aase#13b+RNaseL(F)#23a, 2-5Aase#13b+RNaseL(F)#27a, 2-5Aase#13b+RNaseL(F)#30b)] were sown on MS agar medium containing 100 μg/ml hygromycin to select RNaseL(F)-introduced tobacco. After young plants were potted, DNA was extracted from a part of their leaves. Then, the presence of 2-5Aase cDNA or RNaseL(F) cDNA was confirmed by PCR (see Example 5). To plants about 4 weeks after potting, 15 μg/ml of CMV Y strain was inoculated. Then, the time course after viral infection and the development of disease symptoms were observed. For each of the transformant lines, 5 individuals were used for the inoculation experiment. As a result, necrotic spots were observed 3 days after inoculation in inoculated leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. On the other hand, no necrotic spots were observed in 2-5-Aase-introduced tobacco and RNaseL(F)-introduced tobacco (FIG. 7). Twelve days after inoculation, while disease symptoms were observed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco, no disease symptoms were observed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco (FIG. 8). The total protein was extracted from portions with no necrotic spots in inoculated leaves exhibiting necrotic spots in each transformant tobacco 5 days after infection; and from uninoculated upper leaves of each transformant tobacco 12 days after inoculation by the method described in Example 5, to thereby detect CMV in infected plant leaves. As a result, while a large quantity of CMV was accumulated in inoculated leaves of 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco 5 days after infection, CMV was not detected in non-necrotic spot-forming portions of 2-5Aase+RNaseL(F)-introduced tobacco though a small quantity of CMV was detected in necrotic spots (FIG. 9). Also, in uninoculated upper leaves 12 days after inoculation, while a large quantity of CMV was accumulated in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco, CMV was not detected at all in 2-5Aase+RNaseL(F)-introduced tobacco (FIG. 10). From these results, it is considered as follows: 2-5Aase+RNaseL(F)-introduced tobacco formed necrotic spots in CMV-inoculated leaves and the infected cells died from necrosis to thereby prevent the spreading of virus; thus, no disease symptoms were developed.

EXAMPLE 7 Cucumber Mosaic Virus (CMV Y Strain) Infection Experiment

Using Crude Extract from Infected Leaves as an Inoculum

Using R1 seeds [1 line of 2-5Aase-introduced tobacco (2-5Aase#13b); 2 lines of RNaseL(F)-introduced tobacco (RNaseL(F)#23a, RNaseL(F)#30b)] and F1 seeds [2 lines of 2-5Aase+RNaseL(F)-introduced tobacco (2-5Aase#13b+RNaseL(F)#23a, 2-5Aase#13b+RNaseL(F)#30b)], plants were bred in the same manner as described in Example 6. A crude extract was prepared by infecting a tobacco plant about 2 weeks after potting with CMV Y strain and grinding those tobacco leaves (cv Xanthi nc) exhibiting disease symptoms in 10 times the leaf weight of an extraction buffer (10 mM phosphate buffer, pH 7.0, 20 mM 2-mercaptoethanol). The crude extract was inoculated into tobacco plants about 2 weeks after potting, and the time course after inoculation and the development of disease symptoms were observed. For each of the transformant lines, 2 individuals were used for the inoculation experiment. As a result, similar progress as seen when 15 μg/ml of purified virus was infected in Example 6 was observed. Briefly, necrotic spots were observed 3 days after inoculation in inoculated leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. On the other hand, no necrotic spots were observed in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco. Inoculated leaves 5 days after inoculation are shown in FIG. 11. Twelve days after infection, while disease symptoms were observed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco, no disease symptoms were observed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. Plants 16 days after inoculation are shown in FIG. 12. These results demonstrate that the resistant reaction of 2-5Aase+RNaseL(F)-introduced tobacco against CMV Y strain does not vary depending on the form of an inoculum (i.e., purified virus or crude extract from infected leaves).

EXAMPLE 8 Potato Virus Y T Strain(PVY T Strain) Infection Experiment

Using R1 seeds [1 line of 2-5Aase-introduced tobacco (2-5Aase#13b); 3 lines of RNaseL(F)-introduced tobacco (RNaseL(F)#23a, RNaseL(F)#27a, RNaseL(F)#30b)] and F1 seeds [3 lines of 2-5Aase+RNaseL(F)-introduced tobacco (2-5Aase#13b+RNaseL(F)#23a, 2-5Aase#13b+RNaseL(F)#27a, 2-5Aase#13b+RNaseL(F)#30b)], plants were bred in the same manner as described in Example 6. A crude extract was prepared by infecting a tobacco plant with PVY T strain and grinding those tobacco leaves (cv Samsun) exhibiting disease symptoms in 10 times the leaf weight of an extraction buffer (10 mM phosphate buffer, pH 7.0, 20 mM 2-mercaptoethanol). The crude extract was inoculated into tobacco plants about 2 weeks after potting, and the time course after inoculation and the development of disease symptoms were observed. For each of the transformant lines, 5 to 7 individuals were used for the inoculation experiment. As a result, as seen when CMV Y strain was inoculated, necrotic spots were observed 3 days after inoculation in inoculated leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. On the other hand, no necrotic spots were observed in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco. Inoculated leaves 5 days after inoculation are shown in FIG. 13. Five days after inoculation, necrosis began to be formed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. This necrosis gradually spread and the plants almost completely withered 20 days after inoculation. Plants 14 days after inoculation are shown in FIG. 14. On the other hand, no withered plants were observed in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco. These tobacco plants presented disease symptoms peculiar to PVY T strain.

The total protein was extracted from uninoculated upper leaves of each transformant tobacco 5 days and 10 days after inoculation in the same manner as described in Example 5 to thereby detect the accumulation of PVY T strain. As a result, while the accumulation of PVY T strain was detected in uninoculated upper leaves both 5 days and 10 days after inoculation in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco, no accumulation of PVY T strain was detected in 2-5Aase+RNaseL(F)-introduced tobacco (FIG. 15). From these results, it is considered as follows: necrotic spots were formed in inoculated leaves of 2-5Aase+RNaseL(F)-introduced tobacco and the infected cells died from necrosis; on the other hand, activation of RNaseL has occurred in uninoculated upper leaves also for some unknown reason, which has caused the systemic withering. However, the fact that the accumulation of PVY T strain was not detected in uninoculated upper leaves both 5 days after inoculation when necrosis began to develop and 10 days after inoculation when necrosis was progressing indicates that the immediate cause for the systemic withering was not excessive accumulation of PVY T strain. In the actual scene of agriculture, virus-infected plants are disposed as early as possible in order to avoid the spreading of virus into surrounding plants (secondary infection). The fact that 2-5Aase+RNaseL(F)-introduced tobacco infected with PVY T strain withers without undergoing the process of virus accumulation means that 2-5Aase+RNaseL(F)-introduced plants will not become sources of secondary infection even if they are infected with PVY T strain and that they will wither naturally. Thus, reduction of labor can be expected when such plants are actually cultured.

EXAMPLE 9 Potato Virus Y O Strain (PVY O Strain) Infection Experiment

Using R1 seeds [1 line of 2-5Aase-introduced tobacco (2-SAase#13b); 3 lines of RNaseL(F)-introduced tobacco (RNaseL(F)#23a, RNaseL(F)#27a, RNaseL(F)#30b)] and F1 seeds [3 lines of 2-5Aase+RNaseL(F)-introduced tobacco (2-5Aase#13b+RNaseL(F)#23a, 2-5Aase#13b+RNaseL(F)#27a, 2-5Aase#13b+RNaseL(F)#30b)], plants were bred in the same manner as described in Example 6. A crude extract was prepared by infecting a tobacco plant with PVY O strain and grinding those tobacco leaves (cv Samsun) exhibiting disease symptoms in 10 times the leaf weight of an extraction buffer (10 mM phosphate buffer, pH 7.0, 20 mM 2-mercaptoethanol). The crude extract was inoculated into tobacco plants about 2 weeks after potting, and the time course after inoculation and the development of disease symptoms were observed. For each of the transformant lines, 5 individuals were used for the inoculation experiment. As a result, almost the same results as seen when PVY T strain was inoculated were observed. Briefly, necrotic spots were observed 3 days after inoculation in inoculated leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. On the other hand, no necrotic spots were observed in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco (FIG. 16). Five days after inoculation, necrosis began to be formed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. This necrosis gradually spread and the plants almost completely withered 20 days after inoculation. Plants 15 days after inoculation are shown in FIG. 17. On the other hand, no withered plants were observed in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco. These tobacco plants presented disease symptoms peculiar to PVY O strain.

The total protein was extracted from inoculated leaves of each transformant S days after inoculation and from uninoculated upper leaves of each transformant 6 days after inoculation in the same manner as described in Example 5 to thereby detect the accumulation of PVY O strain. As a result, while PVY O strain was accumulated in both the inoculated leaves 5 days after inoculation and the uninoculated upper leaves 6 days after inoculation in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco, no accumulation of PVY O strain was detected in 2-5Aase+RNaseL(F)-introduced tobacco (FIG. 18). From these results, it was found that although 2-5Aase+RNaseL(F)-introduced tobacco also forms necrotic spots in inoculated leaves due to PVY O strain-infection and the infected cells die from necrosis, this tobacco withers without undergoing the process of virus accumulation. Thus, the nature of 2-5Aase+RNaseL(F)-introduced tobacco that it withers when infected with virus is considered not to vary depending on the strain of PVY but to be a reaction against PVY itself. Not only against infection with PVY T strain but also against infection with PVY O strain, reduction of labor can be expected in the culturing of 2-5Aase+RNaseL(F)-introduced tobacco, and yet this tobacco is considered not to become a source of secondary infection.

EXAMPLE 10 Buffer Inoculation

Using F1 seeds [3 lines of 2-5Aase+RNaseL(F)-introduced tobacco (2-5Aase#13b+RNaseL(F)#23a, 2-5Aase#13b+RNaseL(F)#27a, 2-5Aase#13b+RNaseL(F)#30b)], plants were bred in the same manner as described in Example 6. An extraction buffer (10 mM phosphate buffer, pH 7.0 20 mM 2-mercaptoethanol) was inoculated into plants about 2 weeks after potting, and the time course after inoculation and the development of disease symptoms were observed. For each of the transformant lines, 2 individuals were used for the inoculation experiment. As a result, no change was observed even 10 days after inoculation in both inoculated leaves and uninoculated leaves.

This demonstrates that the series of reactions of 2-5Aase+RNaseL(F)-introduced tobacco after viral infection as described above have been caused by the virus, not by some component(s) in the buffer or the act of inoculation itself.

EXAMPLE 11 Cloning of Bovine-Derived 2-5Aase cDNA and Bovine-Derived RNaseL cDNA and Determination of Their Base Sequences

Phage DNA was extracted from a bovine spleen-derived phage lambda gt10 cDNA library (Clontech) by the method of Xshida et al. (“Gene Expression Experimental Manual”, Chapter 2, published by Kodansha, 1994) and used as a DNA template for PCR. Primers for use In PCR cloning of bovine 2-5Aase and RNaseL cDNA fragments were designed as follows based on the base sequences for human 2-5Aase cDNA (EMBO J., 4. 2249, 1985) and human 2-5RNaseL cDNA (Cell, 72, 753, 1993).

Bovine 2-5Aase:

5′-TCCAAGGTGGTAAAGGGTGGCTCCTCAGGCAA-3′

5′-CTCTGAGCTTGGTGGGGCTGCTTCAGGAA-3′

Bovine RNaseL:

5′-CTGGGGTTCTATGAGAAGCAAGAAGTAGCTGTTGAA-3′

5′-GACAAGTGTAGTTCTTGAACAGCCTTAAATATAGA-3′

A PCR was performed by the method of Ishida et al. and the amplified DNA fragments were subcloned into pBluescript SKII⁺ plasmid (Stratagene) (“Gene Expression Experimental Manual”, Chapter 2, published by Kodansha, 1994). Base sequences for these PCR-amplified DNA fragments (2-5Aase: 455 bp; RNaseL: 292 bp) were determined. These base sequences were compared with the base sequences for human 2-5Aase and RNaseL, respectively. As a result, homology was recognized [2-5Aase: 80%; RNaseL: 73% (sequences for primers were excluded from the calculation)]. Thus, these PCR-amplified DNA fragments were confirmed to be parts of bovine-derived 2-5Aase cDNA and bovine-derived RNaseL cDNA, respectively.

Using these PCR-amplified DNA fragments as probes, the bovine spleen-derived cDNA phage library was screened to thereby isolate phage clones encoding full length 2-5Aase cDNA and RNaseL cDNA, respectively. DNA was extracted from each of the isolated phage clones and subcloned into pBluescript SKII⁺plasmid as a cDNA insert. Using DNA Sequencer 373A from Applied Biosystems, the DNA sequence was determined by the fluorescent dye terminator method, and the amino acid sequence deduced therefrom was obtained (FIG. 19: bovine 2-5Aase cDNA; FIG. 20: bovine RNaseL cDNA). As a result, it was found that bovine 2-5Aase has homology to human 2-5AaseE18 (EMBO J., 4, 2249, 1985) and mouse 2-5AaseL3 (Virology, 179, 228, 1990).

By expressing the thus obtained bovine 2-5Aase cDNA and bovine RNaseL CDNA in plants, it becomes possible to breed virus resistant plants.

EXAMPLE 12 Transformation of Tobacco Cultivar Samsun (Nicotiana tabacum cv Samsun)

Tobacco cultivar Samsun (genotype of N gene: nn) was used for transformation. Transformants [2-5Aase(S) tobacco and RNaseL(S) tobacco] were created by the method described in Example 2 (i.e., by using pBI2-5Aase- or pBIBRNaseL(F)-introduced Agrobacterium LBA4404).

The resultant transformants were potted. Subsequently, R1 seeds were obtained by self-pollination and F1 seeds [2-5Aase(S)+RNaseL(S) tobacco] by crossing.

EXAMPLE 13 Detection of 2-5Aase Activity and RNaseL Activity in 2-5Aase-introduced Transformant Tobacco (Samsun) and RNaseL(F)-introduced Transformant Tobacco (Samsun)

Detection of 2-5Aase activity was performed in the same manner as described in Example 3 and detection of RNaseL activity in the same manner as described in Example 4. The results are shown in FIGS. 21 and 22. Both the 2-5Aase activity in 2-5Aase(S) tobacco and the RNaseL activity in RNaseL(S) tobacco were significantly higher than those in non-transformants.

EXAMPLE 14 Cucumber Mosaic Virus (CMV Y Strain) Infection Experiment on Samsun Transformants Using Crude Extract from Virus-Infected Leaves as an Inoculum

Using R1 seeds [2-5Aase-introduced tobacco (2-5Aase(S)#13-10); RNaseL(F)-introduced tobacco (RNaseL(S)#57-6b)] and F1 seeds [2-5Aase+RNaseL(F)-introduced tobacco (2-5Aase(S)#13-10+RNaseL(S)#57-6b)], plants were bred in the same manner as described in Example 6. A crude extract from CMV Y strain-infected leaves was inoculated into plants about 2 weeks after potting as described in Example 7. The time course after inoculation and the development of disease symptoms were observed. For each of the transformant lines, 3 individuals were used for the inoculation experiment. As a result, similar progress as seen when CMV Y strain was inoculated into Xanthi (genotype of N gene: NN) transformants in Examples 6 and 7 was observed. Briefly, necrotic spots were observed 3 days after inoculation in inoculated leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco. On the other hand, no necrotic spots were observed in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco (FIG. 23). Ten days after inoculation, while disease symptoms were observed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase-introduced tobacco and RNaseL(F)-introduced tobacco, no disease symptoms were observed in uninoculated upper leaves of all the individuals of all the lines in 2-5Aase+RNaseL(F)-introduced tobacco (FIG. 24). These results indicate that the resistant reaction of 2-5Aase+RNaseL(F)-introduced tobacco against CMV Y strain does not depend on the genotype of N gene in the host tobacco.

INDUSTRIAL APPLICABILITY

The 2-5Aase/RNaseL system expresses ribonuclease activity in cytoplasm upon recognition of double-stranded RNA produced when cells are infected with virus, to thereby inhibit viral proliferation. Since RNA viruses generally form double-stranded RNA at the stage of replication, this system is effective against all of the RNA viruses.

Accordingly, the technology of the invention for creating virus resistant plants comprising introducing 2-5Aase and RNaseL into plants by recombinant DNA technology is widely applicable to the breeding of virus resistant plant varieties.

12 1322 base pairs nucleic acid double linear cDNA Human 1 GAGGCAGTTC TGTTGCCACT CTCTCTCCTG TCAATGATGG ATCTCAGAAA TACCCCAGCC 60 AAATCTCTGG ACAAGTTCAT TGAAGACTAT CTCTTGCCAG ACACGTGTTT CCGCATGCAA 120 ATCGACCATG CCATTGACAT CATCTGTGGG TTCCTGAAGG AAAGGTGCTT CCGAGGTAGC 180 TCCTACCCTG TGTGTGTGTC CAAGGTGGTA AAGGGTGGCT CCTCAGGCAA GGGCACCACC 240 CTCAGAGGCC GATCTGACGC TGACCTGGTT GTCTTCCTCA GTCCTCTCAC CACTTTTCAG 300 GATCAGTTAA ATCGCCGGGG AGAGTTCATC CAGGAAATTA GGAGACAGCT GGAAGCCTGT 360 CAAAGAGAGA GAGCACTTTC CGTGAAGTTT GAGGTCCAGG CTCCACGCTG GGGCAACCCC 420 CGTGCGCTCA GCTTCGTACT GAGTTCGCTC CAGCTCGGGG AGGGGGTGGA GTTCGATGTG 480 CTGCCTGCCT TTGATGCCCT GGGTCAGTTG ACTGGCAGCT ATAAACCTAA CCCCCAAATC 540 TATGTCAAGC TCATCGAGGA GTGCACCGAC CTGCAGAAAG AGGGCGAGTT CTCCACCTGC 600 TTCACAGAAC TACAGAGAGA CTTCCTGAAG CAGCGCCCCA CCAAGCTCAA GAGCCTCATC 660 CGCCTAGTCA AGCACTGGTA CCAAAATTGT AAGAAGAAGC TTGGGAAGCT GCCACCTCAG 720 TATGCCCTGG AGCTCCTGAC GGTCTATGCT TGGGAGCGAG GGAGCATGAA AACACATTTC 780 AACACAGCCC AAGGATTTCG GACGGTCTTG GAATTAGTCA TAAACTACCA GCAACTCTGC 840 ATCTACTGGA CAAAGTATTA TGACTTTAAA AACCCCATTA TTGAAAAGTA CCTGAGAAGG 900 CAGCTCACGA AACCCAGGCC TGTGATCCTG GACCCGGCGG ACCCTACAGG AAACTTGGGT 960 GGTGGAGACC CAAAGGGTTG GAGGCAGCTG GCACAAGAGG CTGAGGCCTG GCTGAATTAC 1020 CCATGCTTTA AGAATTGGGA TGGGTCCCCA GTGAGCTCCT GGATTCTGCT GGTGAGACCT 1080 CCTGCTTCCT CCCTGCCATT CATCCCTGCC CCTCTCCATG AAGCTTGAGA CATATAGCTG 1140 GAGACCATTC TTTCCAAAGA ACTTACCTCT TGCCAAAGGC CATTTATATT CATATAGTGA 1200 CAGGCTGTGC TCCATATTTT ACAGTCATTT TGGTCACAAT CGAGGGTTTC TGGAATTTTC 1260 ACATCCCTTG TCCAGAATTC ATTCCCCTAA GAGTAATAAT AAATAATCTC TAACACCAAA 1320 AA 1322 50 base pairs nucleic acid single linear other nucleic acid /desc = “synthetic DNA” not provided 2 TTATTGAAAA GTACCTGAGA AGGCAGCTCA CGAAACCCAG GCCTGTGATC 50 2378 base pairs nucleic acid double linear cDNA human 3 CTTTGATTAA GTGCTAGGAG ATAAATTTGC ATTTTCTCAA GGAAAAGGCT AAAAGTGGTA 60 GCAGGTGGCA TTTACCGTCA TGGAGAGCAG GGATCATAAC AACCCCCAGG AGGGACCCAC 120 GTCCTCCAGC GGTAGAAGGG CTGCAGTGGA AGACAATCAC TTGCTGATTA AAGCTGTTCA 180 AAACGAAGAT GTTGACCTGG TCCAGCAATT GCTGGAAGGT GGAGCCAATG TTAATTTCCA 240 GGAAGAGGAA GGGGGCTGGA CACCTCTGCA TAACGCAGTA CAAATGAGCA GGGAGGACAT 300 TGTGGAACTT CTGCTTCGTC ATGGTGCTGA CCCTGTTCTG AGGAAGAAGA ATGGGGCCAC 360 GCCTTTTATC CTCGCAGCGA TTGCGGGGAG CGTGAAGCTG CTGAAACTTT TCCTTTCTAA 420 AGGAGCAGAT GTCAATGAGT GTGATTTTTA TGGCTTCACA GCCTTCATGG AAGCCGCTGT 480 GTATGGTAAG GTCAAAGCCC TAAAATTCCT TTATAAGAGA GGAGCAAATG TGAATTTGAG 540 GCGAAAGACA AAGGAGGATC AAGAGCGGCT GAGGAAAGGA GGGGCCACAG CTCTCATGGA 600 CGCTGCTGAA AAAGGACACG TAGAGGTCTT GAAGATTCTC CTTGATGAGA TGGGGGCAGA 660 TGTAAACGCC TGTGACAATA TGGGCAGAAA TGCCTTGATC CATGCTCTCC TGAGCTCTGA 720 CGATAGTGAT GTGGAGGCTA TTACGCATCT GCTGCTGGAC CATGGGGCTG ATGTCAATGT 780 GAGGGGAGAA AGAGGGAAGA CTCCCCTGAT CCTGGCAGTG GAGAAGAAGC ACTTGGGTTT 840 GGTGCAGAGG CTTCTGGAGC AAGAGCACAT AGAGATTAAT GACACAGACA GTGATGGCAA 900 AACAGCACTG CTGCTTGCTG TTGAACTCAA ACTGAAGAAA ATCGCCGAGT TGCTGTGCAA 960 ACGTGGAGCC AGTACAGATT GTGGGGATCT TGTTATGACA GCGAGGCGGA ATTATGACCA 1020 TTCCCTTGTG AAGGTTCTTC TCTCTCATGG AGCCAAAGAA GATTTTCACC CTCCTGCTGA 1080 AGACTGGAAG CCTCAGAGCT CACACTGGGG GGCAGCCCTG AAGGATCTCC ACAGAATATA 1140 CCGCCCTATG ATTGGCAAAC TCAAGTTCTT TATTGATGAA AAATACAAAA TTGCTGATAC 1200 TTCAGAAGGA GGCATCTACC TGGGGTTCTA TGAGAAGCAA GAAGTAGCTG TGAAGACGTT 1260 CTGTGAGGGC AGCCCACGTG CACAGCGGGA AGTCTCTTGT CTGCAAAGCA GCCGAGAGAA 1320 CAGTCACTTG GTGACATTCT ATGGGAGTGA GAGCCACAGG GGCCACTTGT TTGTGTGTGT 1380 CACCCTCTGT GAGCAGACTC TGGAAGCGTG TTTGGATGTG CACAGAGGGG AAGATGTGGA 1440 AAATGAGGAA GATGAATTTG CCCGAAATGT CCTGTCATCT ATATTTAAGG CTGTTCAAGA 1500 ACTACACTTG TCCTGTGGAT ACACCCACCA GGATCTGCAA CCACAAAACA TCTTAATAGA 1560 TTCTAAGAAA GCTGCTCACC TGGCAGATTT TGATAAGAGC ATCAAGTGGG CTGGAGATCC 1620 ACAGGAAGTC AAGAGAGATC TAGAGGACCT TGGACGGCTG GTCCTCTATG TGGTAAAGAA 1680 GGGAAGCATC TCATTTGAGG ATCTGAAAGC TCAAAGTAAT GAAGAGGTGG TTCAACTTTC 1740 TCCAGATGAG GAAACTAAGG ACCTCATTCA TCGTCTCTTC CATCCTGGGG AACATGTGAG 1800 GGACTGTCTG AGTGACCTGC TGGGTCATCC CTTCTTTTGG ACTTGGGAGA GCCGCTATAG 1860 GACGCTTCGG AATGTGGGAA ATGAATCCGA CATCAAAACA CGAAAATCTG AAAGTGAGAT 1920 CCTCAGACTA CTGCAACCTG GGCCTTCTGA ACATTCCAAA AGTTTTGACA AGTGGACGAC 1980 TAAGATTAAT GAATGTGTTA TGAAAAAAAT GAATAAGTTT TATGAAAAAA GAGGCAATTT 2040 CTACCAGAAC ACTGTGGGTG ATCTGCTAAA GTTCATCCGG AATTTGGGAG AACACATTGA 2100 TGAAGAAAAG CATAAAAAGA TGAAATTAAA AATTGGAGAC CCTTCCCTGT ATTTTCAGAA 2160 GACATTTCCA GATCTGGTGA TCTATGTCTA CACAAAACTA CAGAACACAG AATATAGAAA 2220 GCATTTCCCC CAAACCCACA GTCCAAACAA ACCTCAGTGT GATGGAGCTG GTGGGGCCAG 2280 TGGGTTGGCC AGCCCTGGGT GCTGATGGAC TGATTTGCTG GAGTTCAGGG AACTACTTAT 2340 TAGCTGTAGA GTCCTTGGCA AATCACAACA TTCTGGGC 2378 51 base pairs nucleic acid single linear other nucleic acid /desc = “synthetic DNA” not provided 4 AATGGGGCCA CGCTTTTTAT CCTCGCAGCG ATTGCGGGGA GCGTGAAGCT G 51 32 base pairs nucleic acid single linear other nucleic acid /desc = “synthetic DNA” not provided 5 TCCAAGGTGG TAAAGGGTGG CTCCTCAGGC AA 32 32 base pairs nucleic acid single linear other nucleic acid /desc = “synthetic DNA” not provided 6 CTCTTGAGCT TGGTGGGGCG CTGCTTCAGG AA 32 35 base pairs nucleic acid single linear other nucleic acid /desc = “synthetic DNA” not provided 7 CTGGGGTTCT ATGAGAAGCA AGAAGTAGCT GTGAA 35 35 base pairs nucleic acid single linear other nucleic acid /desc = “synthetic DNA” not provided 8 GACAAGTGTA GTTCTTGAAC AGCCTTAAAT ATAGA 35 1170 base pairs nucleic acid double linear cDNA bovine CDS 1..1167 9 ATG GAA CTC AGA TAT ACC CCG GCC GGG TCT CTA GAC AAG TTC ATC CAA 48 Met Glu Leu Arg Tyr Thr Pro Ala Gly Ser Leu Asp Lys Phe Ile Gln 1 5 10 15 GTC CAC CTC CTG CCA AAC GAA GAA TTC AGC ACG CAG GTC CAA GAA GCC 96 Val His Leu Leu Pro Asn Glu Glu Phe Ser Thr Gln Val Gln Glu Ala 20 25 30 ATC GAC ATC ATC TGC ACT TTC CTG AAG GAA AAG TGT TTC CGA TGT GCC 144 Ile Asp Ile Ile Cys Thr Phe Leu Lys Glu Lys Cys Phe Arg Cys Ala 35 40 45 CCT CAC AGA GTT CGG GTG TCC AAA GTT GTG AAG GGC GGC TCC TCA GGC 192 Pro His Arg Val Arg Val Ser Lys Val Val Lys Gly Gly Ser Ser Gly 50 55 60 AAA GGC ACG ACC CTC AGG GGA CGA TCA GAT GCT GAC CTC GTC GTC TTC 240 Lys Gly Thr Thr Leu Arg Gly Arg Ser Asp Ala Asp Leu Val Val Phe 65 70 75 80 CTC ACC AAT CTC ACA AGT TTT CAG GAA CAG CTT GAG CGC CGA GGA GAA 288 Leu Thr Asn Leu Thr Ser Phe Gln Glu Gln Leu Glu Arg Arg Gly Glu 85 90 95 TTC ATT GAA GAA ATC AGG AGA CAG CTG GAA GCC TGT CAA AGA GAG GAA 336 Phe Ile Glu Glu Ile Arg Arg Gln Leu Glu Ala Cys Gln Arg Glu Glu 100 105 110 ACA TTT GAA GTG AAG TTT GAG GTC CAG AAA CGG CAA TGG GAG AAT CCC 384 Thr Phe Glu Val Lys Phe Glu Val Gln Lys Arg Gln Trp Glu Asn Pro 115 120 125 CGC GCT CTC AGC TTT GTG CTG AGG TCC CCC AAG CTC AAC CAG GCG GTG 432 Arg Ala Leu Ser Phe Val Leu Arg Ser Pro Lys Leu Asn Gln Ala Val 130 135 140 GAG TTC TAT GTC CTG CCC GCC TTT GAT GCC CTA GGT CAG TTG ACC AAA 480 Glu Phe Tyr Val Leu Pro Ala Phe Asp Ala Leu Gly Gln Leu Thr Lys 145 150 155 160 GGT TAC AGA CCT GAC TCT AGA GTC TAT GTC CGG CTC ATC CAA GAG TGC 528 Gly Tyr Arg Pro Asp Ser Arg Val Tyr Val Arg Leu Ile Gln Glu Cys 165 170 175 GAG AAC CTG AGG AGA GAG GGC GAG TTC TCC CCC TGC TTC ACG GAG CTG 576 Glu Asn Leu Arg Arg Glu Gly Glu Phe Ser Pro Cys Phe Thr Glu Leu 180 185 190 CAG CGA GAC TTC CTG AAG AAT CGT CCA ACC AAG CTG AAG AAC CTC ATC 624 Gln Arg Asp Phe Leu Lys Asn Arg Pro Thr Lys Leu Lys Asn Leu Ile 195 200 205 CGC CTG GTG AAG CAC TGG TAC CAA CTG TGT AAG GAG CAG CTT GGA AAG 672 Arg Leu Val Lys His Trp Tyr Gln Leu Cys Lys Glu Gln Leu Gly Lys 210 215 220 CCA TTG CCC CCA CAA TAT GCT CTG GAG CTT CTG ACG GTC TAT GCC TGG 720 Pro Leu Pro Pro Gln Tyr Ala Leu Glu Leu Leu Thr Val Tyr Ala Trp 225 230 235 240 GAA CAA GGA TGC AAT AAA ACA GGA TTC ATC ACA GCT CAG GGA TTT CAG 768 Glu Gln Gly Cys Asn Lys Thr Gly Phe Ile Thr Ala Gln Gly Phe Gln 245 250 255 ACT GTC TTG AAA TTA GTC CTA AAG TAT CAG AAG CTT TGC ATC TAC TGG 816 Thr Val Leu Lys Leu Val Leu Lys Tyr Gln Lys Leu Cys Ile Tyr Trp 260 265 270 GAA AAG AAC TAT AAC TCT GAA AAC CCT ATT ATT GAA GAA TAT CTG ACG 864 Glu Lys Asn Tyr Asn Ser Glu Asn Pro Ile Ile Glu Glu Tyr Leu Thr 275 280 285 AAG CAA CTT GCA AAA CCC AGG CCT GTG ATT CTG GAC CCG GCG GAC CCT 912 Lys Gln Leu Ala Lys Pro Arg Pro Val Ile Leu Asp Pro Ala Asp Pro 290 295 300 ACA GGA AAT GTT GCT GGT AAA GAC GCA TAT AGC TGG GAA CGG CTT GCA 960 Thr Gly Asn Val Ala Gly Lys Asp Ala Tyr Ser Trp Glu Arg Leu Ala 305 310 315 320 CGA ACG GCT TTG GTC TGG CTG GAT TAC CCG TGC TTT AAG AAA TGG GAT 1008 Arg Thr Ala Leu Val Trp Leu Asp Tyr Pro Cys Phe Lys Lys Trp Asp 325 330 335 GGG TCT CCC GTG GGC TCC TGG GAT GTG TCG CCC CAA GAA CAC AGT GAC 1056 Gly Ser Pro Val Gly Ser Trp Asp Val Ser Pro Gln Glu His Ser Asp 340 345 350 CTG ATG TTC CAG GCC TAT GAT TTT AGA CAG CAC TAT AGA CCC TCT CCA 1104 Leu Met Phe Gln Ala Tyr Asp Phe Arg Gln His Tyr Arg Pro Ser Pro 355 360 365 GGA ATC CAG TTC CAC GGA GGA GCC TCT CCC CAG GTG GAA GAG AAC TGG 1152 Gly Ile Gln Phe His Gly Gly Ala Ser Pro Gln Val Glu Glu Asn Trp 370 375 380 ACA TGT ACC ATC CTC TGA 1170 Thr Cys Thr Ile Leu 385 2157 base pairs nucleic acid double linear cDNA to mRNA bovine CDS 1..2154 10 ATG GAG ACT GAG AGC CAT AAC AAC CCT CAG GAA AGA CCC ACA CCC TCT 48 Met Glu Thr Glu Ser His Asn Asn Pro Gln Glu Arg Pro Thr Pro Ser 1 5 10 15 AGT AAT GGG AAG GCT TCA ATG GGA GAC AAT CAT TCG TTG ATT AAA GCT 96 Ser Asn Gly Lys Ala Ser Met Gly Asp Asn His Ser Leu Ile Lys Ala 20 25 30 GTT AGA GAT GAA GAC ATT GAG TCG GTC CAG CAA TTG CTA GAA AGA GGG 144 Val Arg Asp Glu Asp Ile Glu Ser Val Gln Gln Leu Leu Glu Arg Gly 35 40 45 GCT GAT GTC AAT TTC CAG GAA GAA TGG GGC TGG TCA CCT TTG CAT AAT 192 Ala Asp Val Asn Phe Gln Glu Glu Trp Gly Trp Ser Pro Leu His Asn 50 55 60 GCA GTA CAA GTT GAC AGA GAG GAC ATT GTG GAA CTT CTG CTT AGT CAT 240 Ala Val Gln Val Asp Arg Glu Asp Ile Val Glu Leu Leu Leu Ser His 65 70 75 80 GGT GCT GAG CCT TGT CTG CGG AAG AAG AAT GGG GCC ACT CCC TTC ATC 288 Gly Ala Glu Pro Cys Leu Arg Lys Lys Asn Gly Ala Thr Pro Phe Ile 85 90 95 ATT GCT GGG ATT GTG GGA AAC GTG AAG TTG CTC AAA CTA TTA CTT CCT 336 Ile Ala Gly Ile Val Gly Asn Val Lys Leu Leu Lys Leu Leu Leu Pro 100 105 110 AAA GTA ACA GAT GTC AAT GAG TGT GAT GTT AAT GGC TTC ACA GCT TTC 384 Lys Val Thr Asp Val Asn Glu Cys Asp Val Asn Gly Phe Thr Ala Phe 115 120 125 ATG GAA GCT GCT GTG TAT GGC AAA GTC GAA GCC TTA AGA TTC CTG TAT 432 Met Glu Ala Ala Val Tyr Gly Lys Val Glu Ala Leu Arg Phe Leu Tyr 130 135 140 AAC AAC GGA GCA GAG GTG AAT TTG CAC AGA AAG ACA ATA GAG GAT CAA 480 Asn Asn Gly Ala Glu Val Asn Leu His Arg Lys Thr Ile Glu Asp Gln 145 150 155 160 GAG AGG GTT AAG AAA GGA GGG GCC ACT GCT CTC ATG GAT GCT GCT AGA 528 Glu Arg Val Lys Lys Gly Gly Ala Thr Ala Leu Met Asp Ala Ala Arg 165 170 175 AGA GGG CAT GTA GAT GTC GTA GAG ATC CTC CTT CAT GAG ATG GGG GCA 576 Arg Gly His Val Asp Val Val Glu Ile Leu Leu His Glu Met Gly Ala 180 185 190 GAT GTC AAT GCT CGG GAC AAT AGG GGC AGA AAT GCT TTA ATC TAT GCT 624 Asp Val Asn Ala Arg Asp Asn Arg Gly Arg Asn Ala Leu Ile Tyr Ala 195 200 205 CTT CTG AAC TCT GAT GAT GAG AAG GTG AAA GTG AAA GCN ACT ACT CGC 672 Leu Leu Asn Ser Asp Asp Glu Lys Val Lys Val Lys Ala Thr Thr Arg 210 215 220 CTT CTG CTG GAC TAT AAG GTT GAT GTC AAT GTG AGG GGG GAA GGA AGG 720 Leu Leu Leu Asp Tyr Lys Val Asp Val Asn Val Arg Gly Glu Gly Arg 225 230 235 240 AAG ACG CCG CTG ATC TTG GCA GTG GAA AAG AAG AAC CTG GAT CTG GTG 768 Lys Thr Pro Leu Ile Leu Ala Val Glu Lys Lys Asn Leu Asp Leu Val 245 250 255 CAG ATG CTT CTG GAA CAA ACA GCT ATA GAG ATT AAT GAC ACA GAC AGT 816 Gln Met Leu Leu Glu Gln Thr Ala Ile Glu Ile Asn Asp Thr Asp Ser 260 265 270 GAG GGT AAA ACA GCA CTG CTG CTT GCT GTC GAG CTC AAG CTG AAG GAA 864 Glu Gly Lys Thr Ala Leu Leu Leu Ala Val Glu Leu Lys Leu Lys Glu 275 280 285 ATT GCC CAG TTG CTG TGT CGC AAA GGA GCC AGC ACA AAA TGC GGG GAC 912 Ile Ala Gln Leu Leu Cys Arg Lys Gly Ala Ser Thr Lys Cys Gly Asp 290 295 300 CTC GTC GCA ATA GCG AAG CGC AAT TAT GAC TCT GAC CTT GCA AAG TTC 960 Leu Val Ala Ile Ala Lys Arg Asn Tyr Asp Ser Asp Leu Ala Lys Phe 305 310 315 320 CTT CGC CAG CAT GGA GCT GTA GAA GAC GTT TGC CCT CCT GCT AAA GCC 1008 Leu Arg Gln His Gly Ala Val Glu Asp Val Cys Pro Pro Ala Lys Ala 325 330 335 TGG AAG CCT CAG AGC TCA CGT TGG GGG GAG GCC CTG AAA CAT CTT CAC 1056 Trp Lys Pro Gln Ser Ser Arg Trp Gly Glu Ala Leu Lys His Leu His 340 345 350 AGG ATA TAC CGC CCT ATG ATA GGC AAA CTC AAG ATC TTT ATT GAT GAA 1104 Arg Ile Tyr Arg Pro Met Ile Gly Lys Leu Lys Ile Phe Ile Asp Glu 355 360 365 GAA TAT AAA ATC GCT GAC ACT TCC CAA GGG GGC ATC TAC CTG GGG TTA 1152 Glu Tyr Lys Ile Ala Asp Thr Ser Gln Gly Gly Ile Tyr Leu Gly Leu 370 375 380 TAT GAG GAA CAA GAG GTA GCT GTG AAG CGG TTC CCT AAA GGC AGC ACA 1200 Tyr Glu Glu Gln Glu Val Ala Val Lys Arg Phe Pro Lys Gly Ser Thr 385 390 395 400 CGG GGA CAA AAT GAA GTC TCT TGT TTG CAG AGC AAC CGA GCC AAT GGT 1248 Arg Gly Gln Asn Glu Val Ser Cys Leu Gln Ser Asn Arg Ala Asn Gly 405 410 415 CAC GTG GTG ACG TTC TAT GGC AGT GAG AGC GAC AGG ACC TGT CTG TAT 1296 His Val Val Thr Phe Tyr Gly Ser Glu Ser Asp Arg Thr Cys Leu Tyr 420 425 430 GTG TGC CTT GCC CTG TGT GAG CAC ACG CTG GAG AAG CAC TTG GAC GAC 1344 Val Cys Leu Ala Leu Cys Glu His Thr Leu Glu Lys His Leu Asp Asp 435 440 445 CGC AAA GGA GAG GCT GTG CAA AAC AAG GAA GAT GAA TTT GCC CGC AAC 1392 Arg Lys Gly Glu Ala Val Gln Asn Lys Glu Asp Glu Phe Ala Arg Asn 450 455 460 ATC CTC TCA TCT CTG TTT AAG GCT GTT GAG GAA CTA CAC CGG TCT GGA 1440 Ile Leu Ser Ser Leu Phe Lys Ala Val Glu Glu Leu His Arg Ser Gly 465 470 475 480 TAC ACT CAT CAG GAT CTG CAA CCG CAG AAC ATC TTA ATA GAT TCC AAG 1488 Tyr Thr His Gln Asp Leu Gln Pro Gln Asn Ile Leu Ile Asp Ser Lys 485 490 495 AAT GGT GCT TGC CTG GCA GAT TTT GAT AAA AGC GTC AAG GGG ACT GGA 1536 Asn Gly Ala Cys Leu Ala Asp Phe Asp Lys Ser Val Lys Gly Thr Gly 500 505 510 GAT CCA CAG GAA ATC AAG AGA GAT CTA GAG GCC CTG GGA CTG CTG GTC 1584 Asp Pro Gln Glu Ile Lys Arg Asp Leu Glu Ala Leu Gly Leu Leu Val 515 520 525 CTA TAT GTG GTA AAA AAG GGA AAT GAT TCT TTT GAG ATG CTG AAG AAT 1632 Leu Tyr Val Val Lys Lys Gly Asn Asp Ser Phe Glu Met Leu Lys Asn 530 535 540 CTA AGA ACT GAA GAG TTG ATT GAG CGT TCT CCA GAT AAG GAA ACT CGG 1680 Leu Arg Thr Glu Glu Leu Ile Glu Arg Ser Pro Asp Lys Glu Thr Arg 545 550 555 560 GAC CTC ATT CGG CAT CTG TTA GTC CCT GGG GAC AAT GTG AAG GGC CAT 1728 Asp Leu Ile Arg His Leu Leu Val Pro Gly Asp Asn Val Lys Gly His 565 570 575 CTG AGT GGC CTG CTG GCT CAT CCC TTC TTT TGG AGT TGG GAG AGC CGC 1776 Leu Ser Gly Leu Leu Ala His Pro Phe Phe Trp Ser Trp Glu Ser Arg 580 585 590 TAC CGG ACC CTA CGG GAT GTG GGA AAC GAA TCT GAC ATC AAA ACA CGA 1824 Tyr Arg Thr Leu Arg Asp Val Gly Asn Glu Ser Asp Ile Lys Thr Arg 595 600 605 AAT ACT AAT GGC AAG ATC CTC CAG CTT CTG CAA CCT GAA ACA TCT GAA 1872 Asn Thr Asn Gly Lys Ile Leu Gln Leu Leu Gln Pro Glu Thr Ser Glu 610 615 620 CTT CCA AGT TTT GCC CAG TGG ACA ATT GAG GTT GAC AAA TCT GTG ATG 1920 Leu Pro Ser Phe Ala Gln Trp Thr Ile Glu Val Asp Lys Ser Val Met 625 630 635 640 AAA AAA ATG AAT ACC TAT CAG AAC ACT GTA GGT GAC CTG CTG AAG TTC 1968 Lys Lys Met Asn Thr Tyr Gln Asn Thr Val Gly Asp Leu Leu Lys Phe 645 650 655 ATC CGG AAT GTG GGA GAG CAC ATT AAT GAA CAA AAG AAT ATA GAG ATG 2016 Ile Arg Asn Val Gly Glu His Ile Asn Glu Gln Lys Asn Ile Glu Met 660 665 670 AAG TCA AAA ATT GGA GAA CCT TCC CAG TAT TTT CAG GAG AAA TTT CCA 2064 Lys Ser Lys Ile Gly Glu Pro Ser Gln Tyr Phe Gln Glu Lys Phe Pro 675 680 685 GAT CTG GTC ATG TAT GTC TAT AAA AGA CTA CAG AAC ACA GAA TAT GCA 2112 Asp Leu Val Met Tyr Val Tyr Lys Arg Leu Gln Asn Thr Glu Tyr Ala 690 695 700 AAG CAT TTT CCA AAA AAT CTC AAC CTG AAC AAA CCC GAC GTG 2154 Lys His Phe Pro Lys Asn Leu Asn Leu Asn Lys Pro Asp Val 705 710 715 TGA 2157 389 amino acids amino acid linear protein not provided 11 Met Glu Leu Arg Tyr Thr Pro Ala Gly Ser Leu Asp Lys Phe Ile Gln 1 5 10 15 Val His Leu Leu Pro Asn Glu Glu Phe Ser Thr Gln Val Gln Glu Ala 20 25 30 Ile Asp Ile Ile Cys Thr Phe Leu Lys Glu Lys Cys Phe Arg Cys Ala 35 40 45 Pro His Arg Val Arg Val Ser Lys Val Val Lys Gly Gly Ser Ser Gly 50 55 60 Lys Gly Thr Thr Leu Arg Gly Arg Ser Asp Ala Asp Leu Val Val Phe 65 70 75 80 Leu Thr Asn Leu Thr Ser Phe Gln Glu Gln Leu Glu Arg Arg Gly Glu 85 90 95 Phe Ile Glu Glu Ile Arg Arg Gln Leu Glu Ala Cys Gln Arg Glu Glu 100 105 110 Thr Phe Glu Val Lys Phe Glu Val Gln Lys Arg Gln Trp Glu Asn Pro 115 120 125 Arg Ala Leu Ser Phe Val Leu Arg Ser Pro Lys Leu Asn Gln Ala Val 130 135 140 Glu Phe Tyr Val Leu Pro Ala Phe Asp Ala Leu Gly Gln Leu Thr Lys 145 150 155 160 Gly Tyr Arg Pro Asp Ser Arg Val Tyr Val Arg Leu Ile Gln Glu Cys 165 170 175 Glu Asn Leu Arg Arg Glu Gly Glu Phe Ser Pro Cys Phe Thr Glu Leu 180 185 190 Gln Arg Asp Phe Leu Lys Asn Arg Pro Thr Lys Leu Lys Asn Leu Ile 195 200 205 Arg Leu Val Lys His Trp Tyr Gln Leu Cys Lys Glu Gln Leu Gly Lys 210 215 220 Pro Leu Pro Pro Gln Tyr Ala Leu Glu Leu Leu Thr Val Tyr Ala Trp 225 230 235 240 Glu Gln Gly Cys Asn Lys Thr Gly Phe Ile Thr Ala Gln Gly Phe Gln 245 250 255 Thr Val Leu Lys Leu Val Leu Lys Tyr Gln Lys Leu Cys Ile Tyr Trp 260 265 270 Glu Lys Asn Tyr Asn Ser Glu Asn Pro Ile Ile Glu Glu Tyr Leu Thr 275 280 285 Lys Gln Leu Ala Lys Pro Arg Pro Val Ile Leu Asp Pro Ala Asp Pro 290 295 300 Thr Gly Asn Val Ala Gly Lys Asp Ala Tyr Ser Trp Glu Arg Leu Ala 305 310 315 320 Arg Thr Ala Leu Val Trp Leu Asp Tyr Pro Cys Phe Lys Lys Trp Asp 325 330 335 Gly Ser Pro Val Gly Ser Trp Asp Val Ser Pro Gln Glu His Ser Asp 340 345 350 Leu Met Phe Gln Ala Tyr Asp Phe Arg Gln His Tyr Arg Pro Ser Pro 355 360 365 Gly Ile Gln Phe His Gly Gly Ala Ser Pro Gln Val Glu Glu Asn Trp 370 375 380 Thr Cys Thr Ile Leu 385 718 amino acids amino acid linear protein not provided 12 Met Glu Thr Glu Ser His Asn Asn Pro Gln Glu Arg Pro Thr Pro Ser 1 5 10 15 Ser Asn Gly Lys Ala Ser Met Gly Asp Asn His Ser Leu Ile Lys Ala 20 25 30 Val Arg Asp Glu Asp Ile Glu Ser Val Gln Gln Leu Leu Glu Arg Gly 35 40 45 Ala Asp Val Asn Phe Gln Glu Glu Trp Gly Trp Ser Pro Leu His Asn 50 55 60 Ala Val Gln Val Asp Arg Glu Asp Ile Val Glu Leu Leu Leu Ser His 65 70 75 80 Gly Ala Glu Pro Cys Leu Arg Lys Lys Asn Gly Ala Thr Pro Phe Ile 85 90 95 Ile Ala Gly Ile Val Gly Asn Val Lys Leu Leu Lys Leu Leu Leu Pro 100 105 110 Lys Val Thr Asp Val Asn Glu Cys Asp Val Asn Gly Phe Thr Ala Phe 115 120 125 Met Glu Ala Ala Val Tyr Gly Lys Val Glu Ala Leu Arg Phe Leu Tyr 130 135 140 Asn Asn Gly Ala Glu Val Asn Leu His Arg Lys Thr Ile Glu Asp Gln 145 150 155 160 Glu Arg Val Lys Lys Gly Gly Ala Thr Ala Leu Met Asp Ala Ala Arg 165 170 175 Arg Gly His Val Asp Val Val Glu Ile Leu Leu His Glu Met Gly Ala 180 185 190 Asp Val Asn Ala Arg Asp Asn Arg Gly Arg Asn Ala Leu Ile Tyr Ala 195 200 205 Leu Leu Asn Ser Asp Asp Glu Lys Val Lys Val Lys Ala Thr Thr Arg 210 215 220 Leu Leu Leu Asp Tyr Lys Val Asp Val Asn Val Arg Gly Glu Gly Arg 225 230 235 240 Lys Thr Pro Leu Ile Leu Ala Val Glu Lys Lys Asn Leu Asp Leu Val 245 250 255 Gln Met Leu Leu Glu Gln Thr Ala Ile Glu Ile Asn Asp Thr Asp Ser 260 265 270 Glu Gly Lys Thr Ala Leu Leu Leu Ala Val Glu Leu Lys Leu Lys Glu 275 280 285 Ile Ala Gln Leu Leu Cys Arg Lys Gly Ala Ser Thr Lys Cys Gly Asp 290 295 300 Leu Val Ala Ile Ala Lys Arg Asn Tyr Asp Ser Asp Leu Ala Lys Phe 305 310 315 320 Leu Arg Gln His Gly Ala Val Glu Asp Val Cys Pro Pro Ala Lys Ala 325 330 335 Trp Lys Pro Gln Ser Ser Arg Trp Gly Glu Ala Leu Lys His Leu His 340 345 350 Arg Ile Tyr Arg Pro Met Ile Gly Lys Leu Lys Ile Phe Ile Asp Glu 355 360 365 Glu Tyr Lys Ile Ala Asp Thr Ser Gln Gly Gly Ile Tyr Leu Gly Leu 370 375 380 Tyr Glu Glu Gln Glu Val Ala Val Lys Arg Phe Pro Lys Gly Ser Thr 385 390 395 400 Arg Gly Gln Asn Glu Val Ser Cys Leu Gln Ser Asn Arg Ala Asn Gly 405 410 415 His Val Val Thr Phe Tyr Gly Ser Glu Ser Asp Arg Thr Cys Leu Tyr 420 425 430 Val Cys Leu Ala Leu Cys Glu His Thr Leu Glu Lys His Leu Asp Asp 435 440 445 Arg Lys Gly Glu Ala Val Gln Asn Lys Glu Asp Glu Phe Ala Arg Asn 450 455 460 Ile Leu Ser Ser Leu Phe Lys Ala Val Glu Glu Leu His Arg Ser Gly 465 470 475 480 Tyr Thr His Gln Asp Leu Gln Pro Gln Asn Ile Leu Ile Asp Ser Lys 485 490 495 Asn Gly Ala Cys Leu Ala Asp Phe Asp Lys Ser Val Lys Gly Thr Gly 500 505 510 Asp Pro Gln Glu Ile Lys Arg Asp Leu Glu Ala Leu Gly Leu Leu Val 515 520 525 Leu Tyr Val Val Lys Lys Gly Asn Asp Ser Phe Glu Met Leu Lys Asn 530 535 540 Leu Arg Thr Glu Glu Leu Ile Glu Arg Ser Pro Asp Lys Glu Thr Arg 545 550 555 560 Asp Leu Ile Arg His Leu Leu Val Pro Gly Asp Asn Val Lys Gly His 565 570 575 Leu Ser Gly Leu Leu Ala His Pro Phe Phe Trp Ser Trp Glu Ser Arg 580 585 590 Tyr Arg Thr Leu Arg Asp Val Gly Asn Glu Ser Asp Ile Lys Thr Arg 595 600 605 Asn Thr Asn Gly Lys Ile Leu Gln Leu Leu Gln Pro Glu Thr Ser Glu 610 615 620 Leu Pro Ser Phe Ala Gln Trp Thr Ile Glu Val Asp Lys Ser Val Met 625 630 635 640 Lys Lys Met Asn Thr Tyr Gln Asn Thr Val Gly Asp Leu Leu Lys Phe 645 650 655 Ile Arg Asn Val Gly Glu His Ile Asn Glu Gln Lys Asn Ile Glu Met 660 665 670 Lys Ser Lys Ile Gly Glu Pro Ser Gln Tyr Phe Gln Glu Lys Phe Pro 675 680 685 Asp Leu Val Met Tyr Val Tyr Lys Arg Leu Gln Asn Thr Glu Tyr Ala 690 695 700 Lys His Phe Pro Lys Asn Leu Asn Leu Asn Lys Pro Asp Val 705 710 715 

What is claimed is:
 1. A method of preventing spread of RNA virus from an RNA virus-infected plant into noninfected plants, comprising (A) crossing (i) a first plant that comprises a DNA sequence encoding an animal cell-derived (2′-5′) oligoadenylate synthetase with (ii) a second plant that comprises a DNA sequence encoding an animal cell-derived ribonuclease L and (B) obtaining via step (A) a transgenic plant that comprises a DNA sequence encoding an animal cell-derived (2′-5′) oligoadenylate synthetase and a DNA sequence encoding an animal cell-derived ribonuclease L, such that said transgenic plant undergoes necrosis upon infection with said RNA virus, whereby said transgenic plant has the property of preventing spread of said RNA virus to noninfected plants.
 2. The method of claim 1, wherein the DNA sequence encoding an animal cell-derived (2′-5′) oligoadenylate synthetase is derived from any one of human, mouse, rat or bovine.
 3. The method of claim 2, wherein the DNA sequence encoding an animal cell-derived (2′-5′) oligoadenylate synthetase is a cDNA derived from any one of human, mouse, rat or bovine.
 4. The method of claim 1, wherein the DNA sequence encoding an animal cell-derived ribonuclease L is derived from human or bovine.
 5. The method of claim 4, wherein the DNA sequence encoding an animal cell-derived ribonuclease L is a cDNA derived from human or bovine.
 6. The method of claim 1, wherein the DNA sequence encoding an animal cell-derived (2′-5′) oligoadenylate synthetase is derived from any one of human, mouse, rat or bovine, and the DNA sequence encoding an animal cell-derived ribonuclease L is derived from human or bovine.
 7. The method of claim 6, wherein the DNA sequence encoding an animal cell-derived (2′-5′) oligoadenylate synthetase is a cDNA derived from any one of human, mouse, rat or bovine, and the DNA sequence encoding an animal cell-derived ribonuclease L is derived from human or bovine. 